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arXiv · 2002.08590

Drop freezing: fine detection of contaminants by measuring the tip angle

François Boulogne·Anniina Salonen
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Abstract

In this Letter, we show that the shape of a freezing drop of water can be sensitive to the presence of impurities. We measure the tip angle of water drops frozen on a cold plate. The fine changes in tip angle are robustly captured by our image analysis method, which shows a deviation from that of pure water in solutions with salt (NaCl), polymer (PEG) and surfactant (TTAB) starting at concentrations of $10^{-6}$, $10^{-4}$ and $10^{-6}$ M respectively. The method could be adapted into a portable water purity tester, but the work also highlights the complexity of water freezing as it is influenced by trace concentrations of impurities.

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François Boulogne, Anniina Salonen. 2020-02-20. Drop freezing: fine detection of contaminants by measuring the tip angle. https://doi.org/10.1063/1.5144071

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